The present invention relates to a battery pack that includes a battery, and can perform charges to the battery from a charger and power supply (discharges) to electrically-powered equipment from the battery.
A battery pack attached to electrically-powered equipment such as an electric power tool and an electrically-operating machine and supplying electric power to the electrically-powered equipment is provided with not only a battery but also a control circuit that monitors a battery voltage and a current which flows during a charge and a discharge to and from the battery so as to control the charge and the discharge to and from the battery.
In addition, the battery pack is also provided with a power supply circuit which receives power supply from the battery to generate a power supply voltage for driving the control circuit.
In this type of the battery pack, it is conceivable that, when electric power is supplied from the battery to the power supply circuit (and to the control circuit) at all times, the battery comes into an overdischarged state and becomes deteriorated.
Therefore, one example of the battery pack disclosed in Japanese Unexamined Patent Application Publication No. 2010-162656 is configured to cut off a power supply path to the power supply circuit from the battery when the battery voltage falls below an overdischarge determination voltage.
Further, according to this example, while the battery pack is attached to the charger, a power supply voltage generated in the charger is applied to the power supply circuit in the battery pack through a diode for backflow prevention. Thereby, the battery is inhibited from being overdischarged.